Method of forming concrete panels using electrically heated mold

ABSTRACT

Cast panels for building assembly and erection are formed and cured in accordance with a method and through the use of an apparatus which particularly facilitate high rates of production of such panels and thereby facilitate more economical building construction practices. Fluid materials being cast into panels are received within forms which comprise a cured concrete bed defining a horizontal planar surface maintained at an elevated temperature. Following curing of the fluid materials cast into the forms, stripping of the panels from the form is facilitated by vertically movable side forming members and by bulkheads separating the cured into predetermined panel lengths.

United States Patent [191 Godley [4 1 Sept. 23, 1975 METHOD OF FORMINGCONCRETE PANELS USING ELECTRICALLY HEATED MOLD [75] Inventor: FredDarroll Godley, Charlotte,

[73] Assignee: Modular Wall Systems, Inc.,

Charlotte, NC.

22 Filed: Oct. 6, 1971 21 Appl. No.: 186,837

[52] US. Cl. 264/40; 264/228; 264/333; 264/334 [51] Int. Cl. B28B 23/04[58] Field of Search 264/333, 334, 336, DlG. 46, 264/DIG. 43, 256, 219,229, 231, 40;

[56] References Cited UNlTED STATES PATENTS 915,283 3/1909 Frost 249/1721,008,395 11/1911 Urbink 249/158 X 1,175,011 3/1916 Phillipoff.. 249/129X 1,326,246 12/1919 Young 249/172 1,656,423 l/1928 Copeman..... 264/3331,760,282 5/1930 Pederson 249/129 1,799,529 4/1931 Poetsch 249/1582.550.977 5/1951 Dimock 249/131 X 2,886,876 5/1959 Wilson 264/D1G. 432,997,568 8/1961 Leipold et al.... 219/213 3,204,316 9/1965 Jackson2641334 3,348,802 10/1967 Corbett 249/163 3,649,725 3/1972 Olson264/DIG. 43

FOREIGN PATENTS OR APPLICATIONS 749,124 5/1956 United Kingdom 264/228954,969 4/1964 United Kingdom 249/78 1,582,130 9/1969 France 249/78OTHER PUBLlCATlONS Kingeray, Introduction to Ceramics, Wiley, N.Y.,(1960), pp. 628-640 relied on.

Primary Examiner-Robert F. White Assistant ExaminerWillard E. HoagAttorney, Agent, or Firm-Parrott, Bell, Seltzer, Park & Gibson 57ABSTRACT Cast panels for building assembly and erection are fonned andcured in accordance with a method and through the use of an apparatuswhich particularly facilitate high rates of production of such panelsand thereby facilitate more economical building construction practices.Fluid materials being cast into panels are received within forms whichcomprise a cured concrete bed defining a horizontal planar surfacemaintained at an elevated temperature. Following curing of the fluidmaterials cast into the forms, stripping of the panels from the form isfacilitated by vertically movable side forming members and by bulkheadsseparating the cured into predetermined panel lengths.

3 Claims, 6 Drawing Figures Us aw? pt. 23,1975 Sheet 1 of3 3,907 95 USPatent Sept. 23,1975 Sheet 2 of 3 3,907,951

US Patent Sept. 23,1975 Sheet 3 of 3 3,907,951

METHOD OF FORMING CONCRETE PANELS USING ELECTRICALLY HEATED MOLD Thedevelopment of construction practices which satisfactorily employprecast panels of materials such as concrete has included thedevelopment of arrangements and methods for forming and curing suchpanels. Typically, the arrangements used heretofore provide a formingmeans for receiving fluid materials, such as concrete mixes of Portlandcement orthe like, aggregate and water being cast into panels. Concretedelivered as a fluid material and cast into a'form to produce panelstypically requires some interval of time before curing to such astrength that the panel may be handled as a monolithic structure. Onepractice heretofore fol lowed was to permit the poured concrete toremain in the form until it had cured to the extent required to providethe necessary structural strength. This practice was quickly recognizedas requiring an excessively long time in the form and thereby severlylimiting the production rate of precast panels.

In efforts to decrease the time required to cure a panel, steam and thelike has been introduced into pipes to heat fluid materials being castinto panels. However, the resultant thermal shock on admission of thesteam has required that the forming means employed be constructed ofmetal, usually steel. This reliance upon metallic forming means heatedby steam introduces several difficulties including the need to maintainthe metal forming means in a suitably clean and rust free condition, therelatively high capital cost of such an arrangement, and a lack offlexibility in producing panels having varying characteristics.

It is an object of the present invention to form and cure panels cast ofa fluid material such as concrete mix and the like in accordance with amethod and through the use of an apparatus which overcome thedifficulties and deficiencies of prior practices. In accomplishing thisobject of the present invention, reliance is placed upon use of aforming means defining a lengthy elongate bed which is maintained at anelevated temperature and which may be subdivided lengthwise to producepanels of varying dimensions. Further, the forming means of the presentinvention comprises a cured concrete bed defining a horizontal planarsurface for supporting fluid material being cast into panels, whichcured concretebed may be placed into operation at a capital expendituremarkedly below that required for prior metallic forming means. In usingthe cured concrete bed, the present invention obviates the possibilityof thermal shock damage to the cured concrete bed by maintaining the bedat an elevated temperature.

Yet a further object of the present invention is to form and cure castpanels for building structures by depositing fluid material being castinto a bed maintained at an elevated temperature whereby acceleratedcuring of the panels being formed begins immediately upon pouringthereof.

Yet a further object of this invention is to facilitate the release of acured precast panel from a forming means. In accomplishing this objectof the present invention, reliance is placed upon side forming membersarranged to move vertically for a short distance with the panel beingstripped from the forming means and thereafter to return to the normaloperative position by falling away from the panel being stripped. Inaccordance with this invention, the side forming means return to theoperative position following stripping of the panel from the formingmeans and thereby facilitate more rapid recycling of the forming meansfor production of additional panels. 7 j

Another object of the present invention is to facilitate the productionof panels of any desired lengths through the subdivision of an elongateforming means with bulkhead members. By the positioning'of bulkheadmembers at desired spaced locations, panels of any desired length may beformed in the elongate forming means. Further, the bulkheads dividingadjacent panels, in accordance with this invention, freely release suchpanels to be stripped from the forming bed and thereby facilitate morerapid recycling of the forming means and greater rates of production foreast panels.

Some of the objects and advantages of the invention having been stated,others will appear asthe description proceeds, when taken in connectionwith the accompanying drawings, in which- FIG. 1 is a perspective viewof an apparatus in accordance with this invention, partly broken awayand partly schematic;

FIG. 2 is an enlarged perspective view of a portion of the apparatus inaccordance with this invention, taken generally along the line 2-2 inFIG. 1, showing the forming means as prepared for receiving fluidmaterial being cast into panels;

FIG. 3 is a view similar to FIG. 2, illustrating the stripping of a castand cured panel from, the apparatus of this invention; .1

FIG. 4 is an enlarged perspective view, partially broken away andpartially in section, taken generally along the line 44 in FIG. 1; a k

FIG. 5 is a view similar to FIG. illustrating a further step in themethod of this invention for forming and curing panels; and V FIG. 6 isan exploded perspective view, in reduced scale, of a bulkheadillustrated in FIGS. 4 and 5.

In the detailed description which follows, reference will be had to theillustrative embodiment of this invention shown in the accompanyingdrawings. While the accompanying drawings and the detailed descriptionare set forth in order that this invention may be readily and fullyunderstood by persons skilled in the construetion trades and in theforming and curing of cast concrete panels, it is contemplated thataperson skilled in such arts may apply the present disclosure toapparatus and methods not disclosed in detail herein. For this reason,the accompanying drawings and the following detailed description are tobe taken as,illustrative only and not as limiting upon the scope of thisinvention.

The present invention contemplates the use of forming means generallyindicated at 10 for receiving fluid materials such as concrete mix beingcast into building panels to be used in the erection and assembly ofbuilding structuresfPanels of this general class are known to personsengaged in the construction trades and have been disclosed in variouspreviously issued patents, to which reference may be had for other andfurther disclosures. In accordance .with an important feature ofthe-present invention, the forming means 10 comprises a cured concretebed 11 defining a horizontal planar surface for supporting concretebeing cast into panels as disclosed more fully hereinafter. Preferably,the cured concrete bed 1 1 is of substantial length, as on the order ofto 300 feet long, and is of a width predetermined to produce a desiredmodular panel height, such as 4 feet to .8 feet. For purposes ofaccommodating manufacture of panels using the cured concrete bed 11, aconventional cast concrete building floor 12 may surround the bed 11 ifdesired, with it being preferred that a suitable thermal insulationbarrier 13 be interposed between the surrounding factory floor l2 andthe cured concrete bed 11.

In accordance with an important feature of this invention, the curedconcrete bed 11 has positioned therewithin electrical resistance heatingelements 14, cast in situ during initial formation of the cured concretebed 11. By means of an appropriate electrical or electronic thermostaticcontrol 15 and connection with a source of electrical current, such asconventional line power, the electrical resistance heating elements 14embedded in the cured concrete bed 11 may be maintained at an elevatedtemperature sensed within the bed by the control 15, cooled slowly to anambient temperature, or heated slowly to the desired elevatedtemperature. The heating effect of the electrical resistance elements 14is to be distinguished from the heating effects heretofore obtained bymeans of steam flowing through piping systems, in that the slower rateof change obtained by the electrical heating elements 14 avoids thethermal shock which occurs where steam is employed as a source of heatfor curing of cast concrete.

Extending longitudinally of the cured concrete bed 11 and on either sidethereof are side form means generally indicated at 16. Each of the sideform means 16 includes an elongate stationary support member 18 mountedfrom the work floor 12 to extend adjacent but in spaced relation to thecured concrete bed 11. In the form illustrated,the elongate members 18are of channel cross-section and are supported by spaced triangularupright members 19. Engaging with the channel members 18 are slip sideforms 20 of generally box-like cross-sectional configuration. Each sideslip form 20 has a configured side to form a tongue or groove in a panelcast thereagainst and an elongate projecting lip portion 20a extendingfrom the upper surface thereof to overlie the upper extremity of acooperating channel member 18 (FIG. 2). By means of the engagement ofthe side slip form 20 with the channel member 18, the side forms arenormally maintained in spaced relation one from another extendinglongitudinally of the cured concrete bed 11.

It is to be noted that the dimensions of the side slip forms 20, thecured concrete forming bed 11 and the factory floor 12 are such that thehorizontal planar surface defined by the cured concrete bed 11 iselevated a short distance above the adjacent factory floor 12. Further,the cured concrete bed 11 incorporates side edge reinforcing members 21,such as elongate angle iron members, which extend along the outer upperlongitudinal edges thereof to assist in guarding against impact damageto the bed 11. The side slip forms 20 (when in the position of FIG. 2)terminate closely adjacent the angle member 21 so as to provide a sealthere with against the flow of fluid material being cast and therebyprevent the concrete mix from escaping from the forming means.

It is contemplated that texture may be imparted to a panel being cast inthe forming means of this invention by the inclusion of a form liner. Byway of illustration only, a form liner 22 is shown in FIG. 2 which wouldimpart to a panel cast thereagainst a decorative appearance simulatinghand laid masonry such as brick. While the form liner 22 or othersimilar structures may be preferred for some applications of theapparatus of this invention, it is contemplated that such a form linermay be present or absent as may be desired or considered necessary.

Adjacent each terminal end of the elongate forming means which comprisesthe cured concrete bed 1 1 and the side form means 16 are positionedreinforcement securing bulkhead arrangements generally indicated at 24.In each instance, the reinforcement securing arrangements comprise aplurality of generally upright abutment members 25 which preferablyextend downwardly a substantial distance into the factory floor 12 andare thereby securely anchored against tension forces directedlongitudinally of the cured concrete bed 11. By means of transverseforce distributing member 26, a plurality of cables 28 or the like areaccommodated in extending longitudinally of the cured concrete bed 11.In accordance with conventional prestressed concrete constructionpractices, such cables are disposed in the forming means 10 prior to thecasting of concrete mix thereinto and are placed under longitudinaltension by means of hydraulic jacks or the like before panel castingproceeds.

Prior to pouring concrete mix or the like into the bed 10 to form castpanels, the substantial length of the bed is subdivided longitudinallyby disposition therein of bulkhead means as generally indicated at 29.Each bulkhead means 29 includes upper and lower plate members 30, 31(FIGS. 4-6) and side plate members 33, 34. Each of the side platemembers has a plurality of upwardly opening notches 35 therein, foraccommodation of tensioned reinforcing cables 28 (FIGS. 4 and 5). Inpreparation for casting of panels into the apparatus 10, lower platemembers 31 are positioned along the cured concrete bed 1 l atpredetermined spaced intervals desired for the length of panels to beformed, such as 10 or 20 feet. Thereafter, the side plate members 33, 34are positioned on the lower plate members 31 in generally uprightpositions and upper plate members 30 are assembled with the side membersto form a closed box for each bulkhead means 29. By such formation of aclosed box, introduction of concrete to be cured into the space withinthe bulkhead means 29 is precluded.

Following forming and curing of panels, the upper plate members 30 areremoved to permit access to the cables 28 which are severed to freeadjacent cast panels (FIG. 5).

On stripping of a panel from the apparatus 10 (FIG. 3), the side formmeans 16 and the bulkhead means 29 cooperate to facilitate quick returnof the apparatus 10 to the condition required for the next subsequentcycle of casting. In particular, the side slip forms 20 rise with thepanel being stripped from the bed 11 to such an extent as to free tongueand groove projections and recesses formed in the upper and lower sideedges of the panels. The side slip forms 20 then move outwardly awayfrom the panel and fall back down to the operative position. Similarly,the upper extremities of the side plate members 33, 34 of the bulkheadmeans 29 move away from the ends of the panel, toppling backward to amore nearly horizontal position due to engagement of lower lips 33a, 34athereof with channel members 31a, 31b of the lower plate member 31. Itis to be noted that channel members are also provided on the upper platemember 30 to assure proper spacing of the side plate members 33, 34during casting of a panel.

In practicing the method of the present invention, electrical current isdelivered through the control to the resistance heating elements 14embedded in the cured concrete bed 11, in order to slowly heat the bedto a desired operating temperature such as approximately 180F. Whenslowly heated to such an operating temperature, thermal shock to thecured concrete of the bed 1 1 is avoided while the temperature of thebed is elevated to such a degree as to contribute to accelerated curingof concrete poured thereonto. Reinforcing cables 28 are positioned toextend for the length of the forming bed and are placed under propertension. Bulkhead means 29 are positioned at appropriate spacedintervals to subdivide the length of the elongate bed into individualpanel lengths.

With the bed prepared for casting, suitable concrete delivery equipment(not to be disclosed herein in detail) is traversed from one end of thebed to the other, as along rails 38, 39 extending adjacent the curedconcrete bed 11. Fluid material such as a concrete mix is deposited intothe forming bed, to encase the reinforcing cables 28, to assume theshape imparted by any form liner 22, the side slip forms and thebulkhead means 29. Due to the elevated temperature of the cured concretebed 11, curing of the concrete poured into the bed proceeds more rapidlythan would be the case if ambient temperature alone was relied upon.Thereafter, upon the concrete becoming cured to such a degree as to havethe necessary strength, the cables 28 are cut and individual panels arelifted upwardly from the forming apparatus 10 and transported to aconstruction site or to a storage yard.

In the drawings and specification, there has been set forth a preferredembodiment of the invention, and although specific terms are employed,they are used in a generic and descriptive sense only-and not forpurposes of limitation.

That which is claimed is:

X l. A method of forming and curing cast building assembly panelscomprising the steps of preparing a fluid mix of Portland cement andaggregate; pouring the fluid mix into a horizontal forming apparatusincluding an elongate cured concrete bed having electrical heatingelements embedded therein; supporting the fluid mix on the curedconcrete bed while confining the fluid mix between elongate side formsextending adjacent the cured concrete bed and while dividing the mixinto a plurality of spaced apart, longitudinally aligned discrete panellengths separated transversely by bulkhead s; said dividing includingforming each 'of said bulkheads by supporting a lower plate member onsaid bed, supporting a pair of side members on the lower plate memberand inserting an upper plate member to overly and space apart upperportions of said side members, the side members being movable, uponremoval of the upper plate member, between an upright molding positionand a tilted release position; electrically energizing the embeddedheating elements to heat the cured bed while sensing the temperature ofthe cured bed and controlling energization of the embedded heatingelements in response to sensed temperatures for heating the curedconcrete bed at a rate which avoids spalling thereof by thermal shockwhile accelerating curing of the fluid mix; and continuing to supportthe discrete panels on the cured concrete bed until the mix has cured.

2. The method of claim 1 including longitudinally disposing tensionedprestressing cables in spaced relation extending the length of andparallel to the cured concrete bed before pouring the fluid mix, saidcables passing through said bulkheads, and after curing the mix severingthe prestressing cables at locations within the bulkheads for separatingthe discrete panels one from another.

3. A method of forming and curing cast building assembly panelscomprising the steps of preparing a fluid mix of Portland cement andaggregate; pouring the fluid mix into a horizontal forming apparatusincluding an elongate cured concrete bed having electrical heatingelements embedded therein; supporting the fluid mix on the curedconcrete bed while confining the fluid mix between elongate side formsextending adjacent the cured concrete bed and while dividing the mixinto a plurality of spaced apart, longitudinally aligned, discrete panellengths separated transversely by bulkheads; said dividing includingforming each of said bulkheads by supporting a lower plate member onsaid bed, supporting a pair of side members on the lower plate memberand inserting an upper plate member to overly and space apart upperportions of said side members, the side members being movable, uponremoval of the upper plate member, between an upright molding positionand a tilted release position; electrically energizing the embeddedheating elements to heat the cured bed while sensing the temperature ofthe cured bed and controlling energization of the embedded heatingelements in response to sensed temperatures for heating the curedconcrete bed at a rate which avoids spalling thereof by thermal shockwhile accelerating curing of the fluid mix; continuing to support thediscrete panels on the cured concrete bed until the mix has cured; andthereafter lifting the horizontally disposed cured discrete panels fromthe apparatus while raising the side forms vertically and collapsing thebulkheads to release the panels therefrom.

1. A METHOD OF FORMING AND CURING CAST BUILDING ASSEMBLY PANELSCOMPRISING THE STEPS OF PREPARING A FLUID MIX OF PORTLAND CEMENT ANDAGGEREGATE, POURING THE FLUID MIX INTO A HORIZONTAL FORMING APPARATUSINCLUDING AN ELONGATE CURED CONCRETE BED HAVING ELECTRICAL HEATINGELEMENTS EMBEDDED THEREIN, SUPPORTING THE FLUID MIX ON THE CUREDCONCRETE BED WHILE CONFINING THE FLUID MIX BETWEEN ELONGATE SIDE FORMSEXTENDING ADJACENT THE CURED CONCRETE BED WHILE DIVIDING THE MIX INTO APLURALITY OF SPACED APART, LONGITUDINALLY ALIGNED DISCRETE PANEL LENGTHSSEPARATED TRANSVERSELY BY BULKHEADS, SAID DIVIDING INCLUDING FORMINGEACH OF SAID BULKHEADS BY SUPPORTING A LOWER PLATE MEMBER ON SAID BED,SUPPORTING A PAIR OF SIDE MEMBERS ON THE LOWER PLATE MEMBER ANDINSERTING AN UPPER PLATE MEMBER TO OVERLY AND SPACE APART UPPER PORTIONSOF SAID SIDE MEMBERS, THE SIDE MEMBERS BEING MOVABLE, UPON REMOVAL OFTHE UPPER PLATE MEMBER, BETWEEN AN UPRIGHT MOLDING POSITION AND A TILTEDRELEASE POSITION, ELECTRICALLY ENERGIZING THE EMBEDDED HEATING ELEMENTSTO HEAT THE CURED BED WHILE SENSING THE TEMPERATURE OF THE CURED BED ANDCONTROLLING ENERGIZATION OF THE EMBEDDED HEATING ELEMENTS IN RESPONSE TOSENSED TEMPERATURES FOR HEATING THE CURED CONCRETE BED AT A RATE WHICHAVOIDS SPALLING THEREOF BY THERMAL SHOCK WHILE ACCELERATING CURING OFTHE FLUID MIX, AND CONTINUING TO SUPPORT THE DISCRETE PANELS ON THECURED CONCRETE BED UNTIL THE MIX HAS CURED.
 2. The method of claim 1including longitudinally disposing tensioned prestressing cables inspaced relation extending the length of and parallel to the curedconcrete bed before pouring the fluid mix, said cables passing throughsaid bulkheads, and after curing the mix severing the prestressingcables at locations within the bulkheads for separating the discretepanels one from another.
 3. A method of forming and curing cast buildingassembly panels comprising the steps of preparing a fluid mix ofPortland cement and aggregate; pouring the fluid mix into a horizontalforming apparatus including an elongate cured concrete bed havingelectrical heating elements embedded therein; supporting the fluid mixon the cured concrete bed while confining the fluid mix between elongateside forms extending adjacent the cured concrete bed and while dividingthe mix into a Plurality of spaced apart, longitudinally aligned,discrete panel lengths separated transversely by bulkheads; saiddividing including forming each of said bulkheads by supporting a lowerplate member on said bed, supporting a pair of side members on the lowerplate member and inserting an upper plate member to overly and spaceapart upper portions of said side members, the side members beingmovable, upon removal of the upper plate member, between an uprightmolding position and a tilted release position; electrically energizingthe embedded heating elements to heat the cured bed while sensing thetemperature of the cured bed and controlling energization of theembedded heating elements in response to sensed temperatures for heatingthe cured concrete bed at a rate which avoids spalling thereof bythermal shock while accelerating curing of the fluid mix; continuing tosupport the discrete panels on the cured concrete bed until the mix hascured; and thereafter lifting the horizontally disposed cured discretepanels from the apparatus while raising the side forms vertically andcollapsing the bulkheads to release the panels therefrom.